Release agents for adhesive tapes

ABSTRACT

Pressure-sensitive adhesive material comprising a backing member, a pressure-sensitive adhesive on the front side thereof, and a release coat on the backside thereof comprising poly(amide acids), e.g., poly(N-fatty alkyl amide-acids) of the following recurring formula:   WHEREIN A is a divalent organic radical containing from 2 to 15, preferably 2 to 6, carbon atoms, B is a tetravalent organic radical containing at least 4 carbon atoms, R1 is hydrogen or an alkyl radical containing about 1 to 30 carbon atoms and R2 is an alkyl radical containing about 12 to 30 carbon atoms. When R1 is hydrogen, also provided are the corresponding cyclized imide products and mixtures of the polyamides and polyimides. These poly(amide acids) are formed by the reaction of tetracarboxylic acid dianhydrides and fatty diamines.

United States Patent [191 Schwarcz [4 1 Jan. 21, 1975 RELEASE AGENTS FOR ADHESIVE TAPES [75] Inventor:

[73] Assignee: The First Jersey National Bank,

Jersey City, NJ.

[22] Filed: June 6, 1972 [21] Appl. No.: 260,268

Andor Schwarcz, Niskayuna, NY.

[52] US. Cl. ll7/68.5, 117/76 A, 117/122 P, 117/122 PF, 117/161 A, 117/161 P,

156/309, 260/18 N, 260/47 CP, 260/78 TF,

[51] Int. Cl. C09j 7/04 [58] Field of Search 117/122 P, 122 PF, 122 PA, 117/68.5, 76 A; 260/18 N, 78 TF, 857 PA,

[56] References Cited UNITED STATES PATENTS 3,551,200 12/1970 Stivers 260/78 X 3,590,017 6/1971 Bartell et al. 1l7/68.5 X 3,652,500 3/1972 Peterson 260/78 UX Primary Examiner-William D. Martin Assistant Examiner-Bernard D. Pianalto Attorney, Agent, or Firm-Kenway & Jenney; Kenway & Jenney [57] ABSTRACT Pressure-sensitive adhesive material comprising a backing member, a pressure-sensitive adhesive on the front side thereof, and a release coat on the backside thereof comprising poly(amide acids), e.g., poly(N- fatty alkyl amide-acids) of the following recurring formula:

(i coon o c B c iii A T coon R1 R2 11 Claims, N0 Drawings U.S. Pat.

RELEASE AGENTS FOR ADHESIVE TAPES BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to novel poly(amide acid) and poly(imide acid) compositions and mixtures thereof useful as release agents for pressure-sensitive adhesive tapes.

2. Description of the Prior Art Various polyamide and polyimide resins are de scribed in the prior art, including a large class of nylon type resins prepared from aliphatic dicarboxylic acids and aliphatic diamine There is also a large class of socalled linear polyamides and polyimides which are formed by the reaction of polycarboxylic acids and anhydridesand polyprimary amines. Compounds of this latter type are usually prepared by the reaction of tetracarboxylic acid dianhydrides and primary polyamides and products of this type are disclosed, for example in Nos. 3,094,511, 3,154,524, 3,179,614, 3,502,762 and in the textbook entitled New Linear Polymers by Lee et al, published by McGraw Hill (1968). These linear or wholly aromatic polymers have been found useful in a wide variety of areas including use as a backing member for pressure-sensitive adhesive tapes.

With respect to this specific prior art, U.S. Pat. No. 3,154,524 relates to polyamide resins of this general class produced by the reaction of polyamines and aromatic polycarboxylic acids obtained from certain solvent extracts. These products are said to be particularly useful in protective coatings, structural plastics and the like. In U.S. Pat. No. 3,502,762 polyimide films are provided by the reaction of carboxylic acid dianhydrides and unsubstituted organic polyamines which products are said to be useful, for example as a backing member for normally tacky pressure-sensitive adhesive tapes.

Release coating agents for pressure-sensitive adhesive tapes are, in general, used to prevent, or at least reduce, the transfer of the adhesive mass during unwind from a roll thereof, to the backing member, and to control the unwind tension. A release coat provides suitable release properties only if it is less adherent to the adhesive mass than is the backing member itself. However, the release coat must have sufficient adhesion to the backing member to prevent pick-of thereof by the adhesive mass. And, it must have a suitable amount of adhesion to the adhesive mass otherwise it will unwind too readily when in roll form. Thus, it is seen that a release coating to be suitable must involve a balancing of various desired characteristics. It has been found, however, that with some release agents, although initially good release characteristics are provided; after extended contact with an adhesive mass, particularly at elevated temperatures, undesirable side effects are noted. Thus, the adhesion between the release coat and adhesive mass may be so great as to make unwinding very difficult, if not impossible. Various other disadvantages associated with the use of release agents now known to the prior art are also known.

The present invention provides a pressure-sensitive adhesive tape comprising a novel release coating which is neither disclosed nor suggested in any of the aboveidentified references or any other references of which Applicant is aware. This novel class or release agents, as disclosed hereinafter, provides a pressure-sensitive adhesive tape which unwinds easily after storage even in a warm environment, and the adhesive exhibits substantially unimpaired tack and adhesion.

SUMMARY OF THE INVENTION It is accordingly one object of this invention to provide a novel class of release agents for pressuresensitive adhesive tapes.

A further object of the invention is to provide a novel class of polyamide and polyimide acid compositions formed by the reaction of tetracarboxylic acid anhydrides and substituted fatty diamine compounds.

A still further object of the invention is to provide a pressure-sensitive adhesive tape product comprising a backing member, a pressure-sensitive adhesive and as release agents, therefor, 21 new class of polyamide and polyimide acid compositions, and mixtures thereof. formed by the reaction of certain tetracarboxylic acid dianhydrides and fatty diamines.

Other objects and advantages of the present invention will become apparent as the description thereof proceeds.

In satisfaction of the foregoing objects and advantages, there is provided a novel class of polymeric release agents for pressure-sensitive adhesive tapes, the poly(amide acids) of which may be described by the following general recurring repeating unit:

wherein A is a divalent organic radical having from 2 to 15, preferably 2 to 6, carbon atoms, B is a tetravalent organic radical having at least 4 carbon atoms, R, is hydrogen or an alkyl radical containing about 1 to 30 carbon atoms, and R is an alkyl radical containing about 12 to 30 carbon atoms, said polymers having an intrinsic viscosity of more than about 0.04. Also provided are the resulting poly(imide acids) by cyclization of the poly(amide acids), and mixtures of poly(amide acids) and poly(imide acids) as well as methods for the preparation of the novel polymeric products by the reaction of fatty diamines and tetracarboxylic acid dianhydrides. Further, there are provided novel pressuresensitive adhesive tapes containing these products on the backing member thereof as release agents.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As pointed out above, this invention is concerned with a novel class of polyamide and polyimide acid compositions which have been found to be useful as good release agents for pressure-sensitive tapes. As indicated, these polyamide acid polymers are best defined by the following repeating unit:

wherein B, A, R and R are as defined above. The invention is also concerned with the corresponding cyclic polyimide acid compositions which may be described by the following repeating unit:

COOH 0 ii ia N A N \c I wherein B, A, and R are as defined above. Mixtures of polymers of the polyamide (formula I) and polyimide (formula II) are also included.

The poly(imide acids) of formula ll result when R is hydrogen and the reaction is conducted under such conditions of heat that water is evolved from the molecule of formula I so that cyclization occurs. Obviously, as the heating conditions become more severe, the greater the amount of polyimide is formed. Accordingly, the invention as defined herein covers the polyamides of formula I, the polyimides of formula II, mixtures thereof and specific products falling within generic formulae:

These novel polymeric products are prepared by the reaction of tetracarboxylic acid dianhydrides and N- fatty diamines by reacting in approximately stoichiometric equivalent mixtures with or without a solvent and at temperatures ranging up to 200C.

The tetracarboxylic acid dianhydrides whicy may be used as starting materials are of the formula:

c ll ll 0 wherein B is an organic tetravalent radical containing 4-30, preferably 4-20, carbon atoms and wherein the four carbonyl groups are attached to separate carbon atoms and each pair of carbonyl groups is directly attached to adjacent nuclear carbon atoms. In this formula, B is a tetravalent organic radical selected from the group consisting of aromatic, aliphatic, cycloaliphatic or heterocyclic, combinations of aromatic and aliphatic, and substituted groups thereof. Illustrative of suitable dianhydrides ofthis general class which may be used include the following:

3.3'.4,4'-Bcnzophenonctetracarboxylic dianhydride l,2.3.4-Cyclopentanetetracarboxylic dianhydride l2,4,5-Bcnzenetetracarboxylic dianhydride Tetrah'ydrofuran-2,3,4,5-tetracarboxylic dianhydride l,4,5,8-Naphthalenetetracarboxylic dianhydride 3,4,9,l0-Perylenetetracarboxylic dianhydride 4,4-(2Acetoxy-l ,3-glyceryl bisanhydrotrimelliate) Other dianhydrides which may be used include:

Pyromellitic dianhydride 2,3,6,7-Naphthalene tetracarboxylic dianhydride 3,3',4,4-Diphenyl tetracarboxylic dianhydride l,2,5,6-Naphthalene tetracarboxylic dianhydride 2,2,3,3'-Diphenyl tetracarboxylic dianhydride 2,2-Bis(3,4-dicarboxyphenyl)propane dianhydride 3,4-Dicarboxyphenyl sulfone dianhydride 2,3,4,5-Pyrrolidine tetracarboxylic dianhydride Bis(3,4-dicarboxyphenyl)ether dianhydride Ethylene tetracarboxylic dianhydride, and the like.

These several dianhydrides, as well as other which may be used, are well known in the art, for example. from the prior patents mentioned above.

In the invention, these tetracarboxylic dianhydrides are reacted with a fatty diamine of the formula:

l-INA NH wherein R is hydrogen or a fatty alkyl radical of about 1 to 30 carbon atoms, R is an alkyl radical of about l2 to 30 carbon atoms and A is a divalent radical having from 2 to 15, preferably 2 to 6, carbon atoms, the amino groups being attached to separate carbon atoms. The divalent radical A may be selected from the following groups:

aromatic aliphatic cycloaliphatic combinations of aromatic and aliphatic bridged organic radicals wherein the bridge is oxygen, nitrogen or sulfur, silicon or phosphorus and substituted groups thereof.

The most preferred diamines, however, are the aliphatic diamines wherein A is a divalent aliphatic radical having 2 to about 6 carbon atoms, for example, wherein A is ethylene, propylene, butylene, pentylene and hexylene. Straight or branched chained aliphatic groups as well as substituted derivatives are also within the scope of the invention. Highly preferred radicals as the fatty R, and R groups include palmityl, stearyl, docosanyl or behenyl, and the like as well as any combination thereof. In general, however, it may be siad that the alkyl groups of R and R may any alkyl radical having a straight chain and which contains, in the case of R between 1 and 30 carbon atoms and, in the case of R between 12 and 30 carbon atoms. The following diamines represent highly preferred reactants for forming the compositions of this invention.

N-docosanyl-l ,3-propylene diamine N-stearyl-l ,3-propylene diamine N-stearyl-l,2-ethylene diamine N-stearyl-N'-methyl-l ,2-ethylene diamine N-stearyl trimethylene diamine N-stearyl-l,3-hexylene diamine N-biphenyl trimethylene diamine N,N-distearyl-1,3-propylene diamine As mentioned briefly above, these novel compositions are prepared by contacting approximately stoichiometric equivalent mixtures, or up to about 5lO mole percent excess of either reactant, of the tetracarboxylic acid dianhydride and the fatty diamine, with or without a solvent, for sufficient time to complete the polymerization. It is preferred that the reaction be conducted by dissolving each of the reactants in an inert organic solvent which is a solvent for at least one reactant but preferably both reactants and does not contain functional groups which can enter into the reaction, Organic solvents which may be used are the aromatic hydrocarbon organic solvents including toluene, the isomeric xylenes and benzene; the N,N-dialkyl amides such as N,N-dimethylformamide, N,N- dimethylacetamide, etc. Other solvents which may be used include dimethyl sulfoxide, formamide and the like. Combinations or mixtures of solvents may also be used.

The reaction is generally conducted at an elevated noting maximum polymerization is obtained. Another temperature but preferably at a temperature ranging preferred process comprises dissolving the diamine reafrom 20C. to about 200C. and at atmospheric presgent in one portion ofa solvent and the dianhydride resure although subatmospheric or superatmospheric agent in a econd portion of the same or another so]- pressure may be used. As pointed out above, however, 5 vent, d i i h two l i the temperatures of the reaction has a bearing on the final product obtained when R, is hydrogen. Thus, the maximum permissible temperature will depend on the diamine used, the dianhydride used, the particular solvent, the percentage of polyamide acid desired in the 10 final composition when R, is hydrogen and the minimum period of time desired for the reaction. For most combinations of diamines and dianhydrides falling within the definitions given above, it is possible to form compositions of about 100% polyamide acid by con- The degree of polymerization of the poly(amide acid) is subject to deliberate control. The use of equal molar amounts of the reactants under the prescribed conditions provides poly(amide acids) of very high molecular weight. The use of either reactant in large excess limits the extent of polymerization. However, the scope of the present process encompasses the use of up to 5-10 mole percent excess of either the diamine or the dianhydride. More than 10% excess of either reacducting the reaction below about 75C. However, temtahtd reihhs m an uhdeslrably low molecular weght peratures up to 200C. may be tolerated. Quite obvipro he r ously, when R, is hydrogen, the higher the temperature AS Pointed out above, the P y composlhohs of used the greater the amount of water eliminated in the h n n i n have been found t be extremely useful reaction with the formation of more polyi id f f as release agents for pressure-sensitive adhesive tapes. mula II in accordance with the equation: Thus, a further aspect of the invention comprises :1

COOH (i CIIOOH 40 C -H O c B-CO--N--AN c B u A N l A c COOH H R2 0 R2 wherein B, A and R are as previously defined. When pressure-sensitive adhesive material which includes a R, is hydrogen and the polyimide of formula II is depressure-sensitive adhesive on one side of a backing sired, operation at a temperature of about 90100C. member and the novel release coating agents hereinbeis preferable. fore described on the other side. There may optionally When R, and R in this reaction are both alkyl radibe included a primer coating on the front side or surcals, no cyclization can occur and the product is 100% face of the backing material in order to improve its sur- Of the I (amide acid) 0f fOrmuia face bonding characteristics to the pressure-sensitive he f n p lymeriz Products resulting from this adhesive which is applied thereon. Also, a base coat reaction may be described as having an intrinsic viscosmay b i l d d on th other surface f th b king of more than about and Preferably more than member in order to improve the bonding characterisabout P to 007 as measured in tetrahydmfurah tics of that surface to the release coating composition at applied thereon. The invention is also inclusive of rolls in p hg the hvchtloh a Preferred P Q of pressure-sensitive adhesive tape of suitable width Volves p h equlmolar amounts of the dlamme and length converted from the adhesive material. and the (hahhydnde as dry Sohds and then addmg the The pressure-sensitive adhesive comprises any elasmlxture' m Smah porhohs and Whh agltahoh to the tomeric material such as natural or synthetic rubber,

.gahic i Premhhhg the ingredients and h addexamples of which include polyisobutylene, polybutaing them in small portions to the solvent provides reladiene poWchlorisoPrene, polyisoprene and ethylenetively simple means for controlling the temperature and p py p y p y y F ethers the rate of the process. The reaction 15 exothermic and p y of butadiene and acrylonitrile butadiene and tends to acchlerate very-rapidly It IS Important to regu' styrene, polyacrylates, and other synthetic and natural late the additions to maintain the reaction temperature rubbers or elastomers. The elastomers described may belqh-l the predetermined-WET However the Order of be used separately or in combination The adhesive addition may be varied within the scope of the present invention. After premixing the diamine and the dianhycomposmoh K also mch'de hh Components dride, the solvent may be added to the mixture with agiknown as tacklfymg agents These tacklfymg agents are tation. It is also possible to dissolve the diamine in the usually added m other to P h adhereh ce 9 Surfaces organic solvent, while agitating and preheating the soto h' the tape apphed wlthout P h of h lution to an elevated temperature below or at the pre- Precable pressure- Examples of tacklfylhg agents determined maximum, and then to add the dianhydride Flude polyterpefle Fesms, hydhocartwn resmsi P y at a rate sufficient to control the ultimate maximum redlsprohorhohated r051" f wood r051", oil action temperature. Ordinarily, in this latter process Soluble Phenolic resins and the likethe last portion of the dianhydride is added with part of 1 Other components of the pressure-sensitive adhesive organic solvent. Another possible method involves addinclude fillers, examples of which are clays, diatomaing the reactants to the solvent in small portions, not as ceous earth, silica, talc, zinc oxide, calcium carbonate, a premixture, but alternately; first diamine, then dianetc.; antioxidants, as for example, polyhydric phenols hydride, then diamine, etc. In any event, it is advisable and their alkyl derivatives, diaryl amines, metal chelatto agitate the solution polymerization system after the ng g n and p z r Such as mineral additions are completed until maximum viscosity deolin, liquid p ly n 0r p ly rylate Optionally, primers which improve the bonding characteristics of certain backing material surfaces for better adhesion of the pressure-sensitive adhesive thereto, may be used. These include natural and synthetic elastomers which can be appled in solution or in latex form. Also, the optional base coat for the other surface of the backing member includes both thermoplastic and thermosetting coating resins such as alkyds, vinyls, acrylics, etc.

The pressure-sensitive adhesive is preferably applied to the backing member, which may or may not have a primer coating thereon, in the form of a solvent solution or emulsion. However, it may also be applied as a hot-melt adhesive. The solvent may be any solvent for the particular pressure-sensitive adhesive, including aromatics such as benzene, toluene and xylene, aliphatics such as low boiling naphthas, hexane, pentane and the like, ketones such as methyl ethyl ketone and methyl isobutyl ketone, and chlorinated hydrocarbons such as chlorobenzene, trichloroethylene, ethylene dichloride, and carbontetraehloride. Alcohols and water or other polar solvents may be used when applicable as a solvent or emulsifying medium for the adhesive.

The pressure-sensitive adhesive is generally prepared by dissolving the elastomeric material in a solvent, or dispersing it in an emulsifying solution. To the adhesive mixture may be added the various additives, as for example, the tackifying agent, plasticizer, antioxidant and filler. The components are blended in the solvent or emulsified until smooth. Heat may be required to achieve a uniform solution or dispersion.

The adhesive composition is applied to the backing material (which may first have been coated with a primer coating), by any convenient method, as by calendering, extrusion, kiss roll, coating, etc. The solvent or emulsifying liquid, where the composition contains these, is removed from the adhesive composition by evaporation by heating. The adhesive material is then generally wound on itself for storage and for slitting into rolls of suitable width and length.

The weight of pressure-sensitive adhesive composition (on a dry basis) is preferred to be in the range of between about 0.5-4.0 ounces per square yard of backing member, but may be outside this range if required for specific purposes. The thickness of the backing member is usually greater than 0.5 mil.

Application of the polymeric polyamide and/or polyimide release agents to the surface of the backing member may be by dissolving the polymeric material in a solvent or dispersing it in a carrier and applying this composition to the backing material by means of roll coating or the like. For convenience of handling, a 0.1% weight solution is preferred. The solvent or carrier is removed by evaporation thus leaving a thin film or residue of release agent on the backing member.

As to the backing member, any material ordinarily used for this purpose may be used with the particular material chosen dependent on the end use for the adhesive tape. Examples of suitable backing materials include fibrous and nonfibrous materials which may be made by weaving, compounding, extruding, etc., as for example, backing materials such as paper, cotton and other cellulosic materials, plastics such as acetates, vinyl halides, polyalkylene and polyester films, glass fabrics, metal foils, etc.

The preferred solvents for all of the release agents of this invention are the aromatic hydrocarbons toluene and xylene because their vapor pressure ranges are particularly adaptable to the manufacture of pressuresensitive adhesive tapes. Benzene can be used, but is is somewhat too volatile and solutions of the release agents in benzene evaporate too rapidly and may, at high temperatures, cause difficulty in obtaining a uniform distribution of the release agent on the backing material. It is preferred to add a small amount of di methyl formamdide, dimethyl sulfoxide, or a lower alcohol to the release composition. The amount added may be from /2-20% of the total solvent weight. Other solvents which may be used include tetrahydrofuran, butyl acetate and dioxane.

Since the imidization reaction is catalyzed by heat, when R, is hydrogen, cyclization of the amide structure to the imide structure will occur at least to some extent during preparation of the release agent, especially at temperatures above 50C., and also during drying of the backsize or release composition which is usually at temperatures greater than 50C. The extent of imidization or cyclization in the release composition in general depends on the heat history of the release agent. However, ring closure, i.e., imidization, may also be affected by treating the intermediate polyamic acid with a earboxylic acid anhydride such as acetic anhydride and benzoic anhydride in the presence of a tertiary amine such as N-ethyl morpholine and pyridine. The combination of this treatment followed by heating can sometimes be advantageously used.

The invention will be further illustrated and described by reference to the following specific examples. The proportions here and elsewhere are expressed as parts by weight unless specifically stated to the contrary.

EXAMPLE I N-biphenyl trimethylenediamine, 20.5 grams (0.05 mol) was dissolved in 200 ml toluene. Then 3,3',4,4- benzophenone tetracarboxylic dianhydride, 16.1 grams (0.05 mol), was added to the solution and refluxed for 2 hours. Infrared spectra of a sample taken showed complete reaction. The product was precipitated in 1.5 liters of methanol, filtered, washed with methanol and dried in a vacuum oven at room temperature. Yield: 32.1 grams (87.6%), transition points by differential thermal analysis (DTA): 176C. and 67C., intrinsic viscosity in tetrahydrofuran: 0.067.

A 1 mil thick Mylar A poly(ethyleneteraphthalate), film was backsized with a 1% toluene solution of the polymer, using a 1 inch diameter bar tightly wound with a 5 mil thick wire. The solvent was evaporated in a forced air oven at 200F. By using this same technique the uncoated side of the film was then primed with a 10% toluene-acetone (6:1) solution of the following composition:

Nitrile Rubber parts by weight Chloroprene 40 parts by weight Zinc Resinate 60 parts by weight The primed side was then coated with a 32% dispersion in toluene of a pressure-sensitive adhesive, at 1.2 ounces (dry) per square yard, of the following composition, using a reverse roll technique and driving the solvent off at 240F.:

Parts by Weight Natural Rubber 25 Polyisoprene O Styrene-Butadiene Rubber 25 Zinc Oxide 50 Petroleum Hydrocarbon Resin 70 Dehydroabietic Acid Alkylated Phenolic Resin 7 Oil Plasticizer 40 Antioxidant 2 The adhesive material was then wound upon itself (60 yards) and slit into rolls 1 inch wide. Prior to testing, the rolls were submitted to accelerated aging as follows:

Temperature Aging (TA): Forced air oven at 150F.

for 16 hours.

TA-72F., 50% RH. for 24 hours, oven at 150F., 85% relative humidity, oxygen atmosphere, inch mercury pressure, 2.5 hours.

Cycle Aging:

Physical testing of the aged rolls yielded the following results:

"PressurmSensitivc Tape Council Test, PSTC-tl. The force required to remove the tape from the roll at 150 ftlminr PSTC-l 180 angle peel.

"PSTC-5 The force resisting peeling of a tape at a 90 angle from a standard surface upon which it has been applied under no other pressure than the weight of the tape itself,

EXAMPLE ll N-biphenyl trimethylenediamine, 20.5 grams (0.05 mol), dissolved in 150 ml toluene, was added dropwise at room temperature to a stirring solution of cyclopentane tetracarboxylic acid dianhydride, 10.5 grams, dissolved in 50 ml N,N-dimethylformamide. After stirring for 16 hours at room temperature, the poly(amide acid) product was precipitated in 1 liter of methanol, filtered, washed with methanol and dried at room temperature under vacuum. Yield 25.7 (83%), softening point 165-172C., intrinsic viscosity in tetrahydrofuran: 0.049.

Rolls of pressure-sensitive adhesive tapes were prepared the same way as described in Example 1, except for the release agent, which was, in this case, prepared with the cyclopentane tetracarboxylic dianhydride. The following unwind adhesion results were obtained:

1 week shelf aging: 0.6 lbs/in. Cycle Aging: 0.5 lbs/in. 9 months shelf aging: 0.5 lbs/in,

EXAMPLE lll N-Biphenyl trimethylenediamine, 20.5 grams (0.05 mol), was added to 3,3,4,4'-benzophenone tetracarboxylic dianhydride, 16.1 grams (0.05 mol). dissolved in the solvent mixture of 150 ml N,N-dimethyl formamide and 30 ml toluene. Infrared analysis taken after 16 hours stirring showed complete reaction. by the disappearance of the 1780 cm band characteristic of anhydrides and the appearance of strong bands at 1600l660 cm and 1720 cm characteristic of am ides and carboxylic acid, consecutively. The solute was isolated by precipitation into two liters of methanol; it was filtered, washed with methanol, and dried in a vacuum oven at room temperature. The poly(amide acid) had the following properties: Softening point 165170C., intrinsic viscosity in tetrahydrofuran 0.060, acid equivalence: 389 g/mol.

A strapping tape coated with a pressure-sensitive adhesive was prepared as follows: A /2 mil Mylar polyester film was backsized with a 1% toluene solution ofthe above polymer and primed, all as in Example 1. It was then coated on the primed side with 1.0 oz./sq. yd. (dry) adhesive of the following composition and the solvent driven off at 240F.:

Parts by Weight Natural Rubber Butadiene-Styrene Copolymer l5 Polyterpene Resins 80 Alkylated Phenolic Resin 12.5 Antioxidant 2 Solvent Mixture (Aliphatic and Aromatic Hydrocarbons) 580 A glass cloth having 100 warp yarns per inch and 8 fill yarns per inch was coated with 3.25 oz./sq. yd. (dry) of the above adhesive and the uncoated side of it was laminated against the mass-coated side of the Mylar film previously prepared. The glass reinforced adhesive material was then slit into 1 inch X 60 yd. rolls and cycle aged. On testing, unwind adhesion was found to be 2.2 lb./in. A tape similarly made but with a commercially available backsize yielded higher than 5 lb./in. unwind adhesion and often delaminated on unwinding.

EXAMPLE 1V N-biphenyl trimethylenediamine, 153.8 grams (0.375 mol), was melted in a 3-necked, round bottom flask equipped with an electrical heater, a stirrer, a Dean-Stark condenser and a nitrogen inlet. The diamine was then dissolved in 700 grams of toluene, the temperature raised to -100C., and 126.8 grams (0.393 mol) of 3,3,4,4-benzophenone tetracarboxylic dianhydride were slowly stirred in. The reaction mixture was refluxed under a slow nitrogen stream for be hour to yield a viscous solution. The amount of water trapped in the Dean-Stark condenser was about 0.5 ml.

65 200 Grams of toluene, and 50 grams of N,N-dimethyl formamide were added which greatly reduced the viscosity. The product was then precipitated in 5 liters of acetone, filtered, washed with acetone and dried in a vacuum oven at 60C. to yield 251.9 grams (90%) of a polymer having the following properties: lntrinsic viscosity in toluene-N,N-dimethylformamide (90:10 by volume): 0.057, acid equivalence: 530 g/mol.

An amine salt solution was formed by dissolving at 60C. 240 grams of the polymer in 2097 grams of water containing 67 grams of morpholine.

This solution was blended, at the level of 2 and 3 dry parts per 100 dry parts, with a latex blend containing a major amount of polyvinylchloride and a minor amount of nitrile rubber. It was then thickened with sodium polyacrylate to yield a release backsize of 500 cps. viscosity.

A crepe paper having a basis weight of 27 lb. per ream was saturated with an SBR latex to a 50% dry pickup. It was coated with the release backsize at 0.47 oz/sq. yd. (dry) using an air knife, dried at 200F. and the backsize fused at 350F.

The backsized sheet was then coated at 1.45 oz/sq. yd. (dry) with the adhesive mass described in Example 1, dried at 240F. and slit to 1 inch X 60 yd. rolls. A similar tape was prepared by using a typical release agent available commercially. The results are summarized in the following table.

Release Agent of ple l with the release agent. the preparation of which is described in Example IV. The backsize had the following wet composition:

Release Agent 1 Toluene 9} N.N-Dimethylformamide 5 The glass cloth side of the laminate was then coated with the following adhesive composition. dispersed in water, and having a total solids content of 45%:

Parts by Weight Natural Rubber 70 Styrene-butadiene rubber Synthetic Polyterpene 65 Sulfur Curative 1 Butyl Zimate 1 Thickener 1 Emulsifier 1 Commercial "parts dry release agent per 100 dry parts of latex backsize.

"150F. air oven. 6 days.

150F. oven. 8591 R.H.. oxygen atmosphere. 20 in. mercury pressure.16 hours. "11)0F.. 85% R.H.. 6 days.

'Delaminarions (paper splitting).

Release Agent Commerical Release of this Example Agent Unwind Adhesion. lb./in.

Cycle Aging 2.8 9.3 8.5

Oxygen Wet Aging 3.8 D D* Adhesion to Stainless Steel (TA) Aged. oZ./in. 41 40 41 Quickstick, (TA) Aged, oz/in. 20 19 20 Cannot unwind without delamination (destruction of the sandwich structure). Unwind values higher than 10 lh./in.

EXAMPLE V A 1.2 mil cellulose acetate film was coated with a laminating cement having the following composition:

Parts by Weight Nitrile Rubber 16.0 Chloroprene 6.4 Zinc Resinate 9.6 Toluene 61 .2 Acetone 6.8

EXAMPLES VI AND Vll Toluene, 12,204 grams and N-biphenyl trimethylene diamine, 3,860 grams (10 moles). were charged in a steam jacketed reactor equipped with a stirrer. a Dean- Stark condenser. a thermometer, and a vacuum pump. Water was taken off at 200F, 15 mm Hg. vacuum for one hour, and 1,356 grams N,N-dimethylformamide was charged in the reactor. While maintaining the temperature at 200F., 3,445 grams (10.5 moles) of 3.3,4,4-benzophenone tetracarboxylic dianhydride was stirred into the reaction mixture over a period of V2 hour. The imidization reaction was continued at 200F, 15 mm Hg. vacuum, by taking off water for the number of hours as specified below, cooling the solution to' 130F., and thinning it by the addition of 1,356 grams of methanol. The polymers which were retrieved by precipitation in acetone and spray drying possessed the following properties:

Example Vl Example Vll Reaction Time, hours I 3.2

Acid Equivalence, 483 642 glmole COOH Conversion to imide, 33 72 lntrinsic Viscosity (in Toluene/DMP 90/10 0.063 0.066

by weight) General purpose pressure-sensitive adhesive tapes were prepared as in Example IV using 2 parts of release agent per 100 parts (dry) of the latex. A similar adhesive tape was prepared by using 5 parts ofa commercial release agent per 100 parts (dry) of the latex. The results* are summarized in the following table:

*The measuring unit and the aging conditions are the same as the ones described in Example IV.

Release Agent of 1. N-Stearyl trimethylene diamine 2. N-Biphenyl trimethylene diamine 3. Benzophenone tetracarboxylic dianhydride 4. Pyromellitic dianhydride 5. 4,4-(2-acetoxy-1,3-glyceryl) bisanhydrotrimellitate From the data shown in the examples it is apparent that the release agents of this invention provide very good unwind adhesion while retaining good adhesion and quickstick to a variety of substrates.

The invention has been described herein by reference to certain preferred embodiments. However, as variations thereon will appear to those skilled in the art, the invention is not to be considered as limited thereto. Moreover, although the invention has been more particularly described for use as a release coating for pressure-sensitive adhesive tape, it will be appreciated that it has many other uses including, among other things, use as a water repellant coating in paper, textile, and metal finishing; an internal and external lubricant for plastics; an antiblock and slip agent for inks and coat- Commercial Example Vl Example Vll Release Agent Unwind Adhesion Cycle Aging 1.1 1.1 16 Dry Aging 0.9 1.0 1.6 Oxygen Wet Aging 1.4 1.4 2.3 Wet Aging (3 days) 1.6 1.6 2.0 Adhesion to Stainless Steel 39 40 38 Quickstick 23 21 20 EXAMPLES Vlll-X Three release polymers were prepared and used in pressure-sensitive adhesive tapes, all as in Examples VI and VII. The various dianhydrides and diamines used, the reaction times, the properties of the polymers and the tapes prepared with these polymers are presented in the following tables:

ings; viscosity increaser and pour point depressant in lubricating oils; and wire coatings.

What is claimed is:

l. Pressure-sensitive adhesive material comprising a backing member, a pressure-sensitive adhesive on the front side thereof, and a release coat on the backside thereof comprising a polymeric composition of the gen- 40 eral recurring formulae:

I plat release agent per 100 parts latex blend [\ll') l. The commercial release agent was 5 phr. blended per 100 parts latex blend (dry).

OOH

Ill. mixtures thereof wherein A is a divalent organic radical having from 2 to 15 carbon atoms, B is a tetravalent radical having at least 4 carbon atoms, R is an alkyl radical containing about 1 to carbon atoms or hydrogen and R is an alkyl radical containing about 12 to 30 carbon atoms the polymeric materials having an intrinsic viscosity of more than about 0.04 as measured in tetrahydrofuran at 30C.

2. Pressure-sensitive adhesive material according to claim 1 wherein B is and organic tetravalent radical containing at least 4 carbon atoms and is selected from the group consisting of aromatic, aliphatic, cycloaliphatic, heterocyclic, combinations of aromatic and aliphatic and substituted groups thereof.

3. Pressure-sensitive adhesive material according to claim 2 wherein A is selected from the group consisting of aromatic, aliphatic, cycloaliphatic, combinations of aromatic and aliphatic, bridged organic radicals wherein the bridge is oxygen, nitrogen, sulfur, silicon or phosphorus, and substituted groups thereof.

4. Pressure-sensitive adhesive material according to claim 1 wherein the release coat comprises a composition of the following recurring formula:

5. Pressure-sensitive adhesive material according to claim 1 wherein the release coat comprises a composition of the following recurring formula:

compounds of formulae 1 and ll.

7. Pressure-sensitive adhesive material according to claim 1 wherein B is selected from the group consisting of naphthyl, diphenyl, alkyl, diphenyl sulfonyl. pyrrolidyl, and diphenyl ether.

8. Pressure-sensitive adhesive material according to claim 7 wherein A is a divalent aliphatic hydrocarbon radical having 2 to about 6 carbon atoms.

9. Pressure-sensitive adhesive material according to claim 1 in which the release coat comprises as a minor component an amine salt of the polymeric composition blended with as a major component a latex blend containing a major amount of polyvinylchloride and a minor amount of nitrile rubber.

l0. Pressure-sensitive adhesive material comprising a backing member, a pressure-sensitive adhesive on the front side thereof, and a release coat on the backside thereof comprising as a minor component a polymeric composition of the general recurring formulae:

lll. mixtures thereof wherein A is a divalent organic radical having from 2 to 15 carbon atoms, B is a tetravalent radical having at least 4 carbon atoms, R, is an alkyl radical containing about 1 to 30 carbon atoms or hydrogen and R is an alkyl radical containing about 12 to 30 carbon atoms, the polymeric materials having an intrinsic viscosity of more than about 0.04 as measured in tetrahydrofuran at 30C. and as a major component a latex blend containing a major amount of polyvinylchloride and a minor amount of nitrile rubber.

ll. Pressure-sensitive material according to claim 10 wherein the amount of said polymeric material in the release coat is at least 2 parts per parts latex blend (dry).

Patent No. 3 86],, 956 Dated Jan 2]. 1975 Q Inventor(5 AndOl ochwarcz It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

The Assignee "The First Jersey National Bank" should be --Nashua Corporation.

The Attorney, Agent or Firm "Kenway 5; Jenney; Kenway 3:

Jenney" should be --Kenway & Jenney--..

In column 4, line 36, the word "siad" should be In column 5, line 64, after the word "of" insert --=the--a In column 7, line 5, the word "appled" should be --=applled--,

Page 2 UNI'IILH S'l./\'l']')l" lA'l'llN'l' UFFHII'I I I (JECH'H HEATH 1H? (JUlHHfAJl ION '2 D Patent No. 3,861,956 Dated J 7] 1975 i lnventofls) Andor Schwarcz It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In column 13. under the first table, the wotd "glmole" should be g/mole In column 13, under the first table, the word "toluene/BM should be 5 --toluene/DMF-.

In column 15, line ll, the word "and" should be g 3 4 UNl'lldl) S'lfAlldIi; lA'll'lN'l' (nu-m;

C I; R'l I F [GATE 0 l C0 .li RE (31 [0 N Patent No. 3 v 956 Dqted 1975 Inventor(s) Andor SCI'LUEICZ It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In column 16, under the second foitmula;

" 0 coon 9 j ,6." I v II. ..-.c ..B a A C i. I R2 9 should be e e 1 "*"1 j 0 goon ,0 l i ---II. c .B/ N.-. A N 1 *0. i

Signed and Scaled this fif Dayof August197; [sun Arrest:

Rum c. MASON :fllt'sling Officer CERTIFICATE OF CORRECTION PATENT NO. 3,861,956 DATED 1 January 21 1975 INVVENTOR(S) I Andor Schwarcz ltis certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

PATENT OFFICE ERRORS In column 1 line 66' the word "or" should read In column 8, line 9 the word "formamdide" should read --formamide-- In column 8, line 35 the word "N-biphenyl" should read --N-behenyl-.

In column 9, line 51, the word "N-biphenyl" should read -N-behenyl-- In column 10 lines 9 and 54 the word "N-biphenyl" should read --N-behenyl--.

In column 12 line 55 the word "N-biphenyl" should read --N-behenyl- I Signed and Scaled this sixteenth Day Of December 1975 [SEAL] AIICSI.

v RUTH C. MASON Arresting Officer C. MARSHALL DANN Commissioner uj'Parents and Trademarks 

2. Pressure-sensitive adhesive material according to claim 1 wherein B is and organic tetravalent radical containing at least 4 carbon atoms and is selected from the group consisting of aromatic, aliphatic, cycloaliphatic, heterocyclic, combinations of aromatic and aliphatic and substituted groups thereof.
 3. Pressure-sensitive adhesive material according to claim 2 wherein A is selected from the group consisting of aromatic, aliphatic, cycloaliphatic, combinations of aromatic and aliphatic, bridged organic radicals wherein the bridge is oxygen, nitrogen, sulfur, silicon or phosphorus, and substituted groups thereof.
 4. Pressure-sensitive adhesive material according to claim 1 wherein the release coat comprises a composition of the following recurring formula:
 5. Pressure-sensitive adhesive material according to claim 1 wherein the release coat comprises a composition of the following recurring formula:
 6. Pressure-sensitive adhesive material according to claim 1 wherein the release coat comprises mixtures of compounds of formulae I and II.
 7. Pressure-sensitive adhesive material according to claim 1 wherein B is selected from the group consisting of naphthyl, diphenyl, alkyl, diphenyl sulfonyl, pyrrolidyl, and diphenyl ether.
 8. Pressure-sensitive adhesive material accOrding to claim 7 wherein A is a divalent aliphatic hydrocarbon radical having 2 to about 6 carbon atoms.
 9. Pressure-sensitive adhesive material according to claim 1 in which the release coat comprises as a minor component an amine salt of the polymeric composition blended with as a major component a latex blend containing a major amount of polyvinylchloride and a minor amount of nitrile rubber.
 10. Pressure-sensitive adhesive material comprising a backing member, a pressure-sensitive adhesive on the front side thereof, and a release coat on the backside thereof comprising as a minor component a polymeric composition of the general recurring formulae:
 11. Pressure-sensitive material according to claim 10 wherein the amount of said polymeric material in the release coat is at least 2 parts per 100 parts latex blend (dry). 